DIY 2cc coupler and calibrated microphone. Besides the bass roll off (which is compensated for with the RETC compensation), it's actually quite accurate (in comparison to Rin and Tyll's graphs raw; compensation used is similar to Rin's).

As requested, the frequency graph. The colored ones are the compensated graphs (for Diffuse Field and my bass roll off), the grey is the raw measurement.

That sudden drump from the 5 kHz region seems to be popular in Dunu's IEMs as well, which gives them a distinct sound, one that these IEMs have as well in the upper vocals.

I'll also attach the MEE A161 for comparison to Tyll and Rin's graph as my DIY cheap setup hasn't been verified too much in public yet. Keep in mind that my system isn't 100% perfect or fool proof. But it'll give you a good idea about sound.